Coil and method of making the same



Oct. 16, 1934. J. c. SNELL COIL AND METHOD OF MAKING THE SAME FiledMarch 7, 1932 Patented Oct. 16, 1934 COIL AND METHOD OF MAKING THE SALEJames C. Snell, Oak Park, Ill., assignor of seventy filer cent to BarryW. Nordendale, Chicago,

Application March 7, 1932, Serial No. 597,153

15 Claims. (Cl. 175-359) This invention relates to coils generally andfacilitates the winding operation of the coil on more particularly tocoils having a plurality of a manual machine as to place such manner ofwindings such as the coils employed in radio production substantially ona competitive basis loud-speaker transformers. with automatic machineproduction of the former Radio loud-speaker transformers are generallycoils. 60

constructed with a. shell-type core and with the More particularly it isan object of the invenprimary and secondary windings formed into 8. tionto provide a novel and compact coil which single coil mounted on thecentral leg of the core. may be constructed on a single machine in acon- The axial length and the radialthickness of the tinuous series ofoperations, of which the formacoil thus directly determine,the length ofthe tion of the core is the first. 65 legs and the spacing of the outerlegs of the core Resulting directly from the ability to produce from thecentral leg, thereby controlling the overmanually wound coils on acommercial basis, is all size of the core. If, then, the coil is undulya coil having the low impedance winding on the large not only does abulky and cumbersome inside and the high impedance winding on thetransformer result, but the cost is raised because outside whichconstruction also constitutes an 70 of the increased amount of steelrequired, and object of the invention. the length of the flux path isincreased. A further object is the provision in a coil of Necessarilythe transformer must have a certhe character described of novel meansfor securtain capacity and a fairly constant ratio of transing andbringing out the leads from the windings.

0 formation which thus requires a minimum num- Other objects andadvantages will become ap- 75 her of turns in the primary and secondarywindparent from the following description taken in ings. Where the coilsare wound on, automatic connection with the accompanying drawing, in orsemi-automatic machines they are wound on which:

v a long preformed core, later severed between each Figure 1 is an endelevational view of a coil emcoil. Because of the amount of timerequired to bodying the features of the invention.

set up and adjust an automatic machine prepara- Fig. 2 is an enlargedvertical sectional view tory to a winding operation onlythe high imtakenalong line 22 of Fig. 1. pedance winding, which is composed of hundredsFig. 3 is a perspective view of the coil of Fig. 1 of turns, is wound onsuch an automatic machine. partially broken away to show the manner ofse- The low impedance winding is later wound over curing and bringingout the leads of the inner 85 the high impedance winding on a manualmawinding. chine and after the core has been severed. More- Fig. 4 is aperspective view showing the manner over, to avoid cutting any turns ofthe coil in the of securing and bringing out the leads of the outersevering of the core, the core is permitted to prowinding.

ject beyond the windings a substantial distance For purposes ofillustration the invention is 90 at both ends thereby increasing thelength of the herein shown embodied in a coil adapted for use coil. Theradial thickness of the coil is increased in a radio speakertransformer. The coil combecause of the fact that machine wound coilsprises generally a. low impedance winding 5 havdepend upon the rigidityof the coil to retain the ing a comparatively small number of turns and40 end turns in position, which rigidity is obtained generallyconstituting the secondary winding of 95 by the insertion of a sheet ofpaper or the like the transformer, a high impedance winding 6 betweeneach layer of turns of the winding. It having a large number of turnsand constituting is thus apparent that much of t e coil 50 contheprimary, and a body structure which supports structed is electricallyinefiective and serves only and bind the windings in position d i hi h oi c s t s of the coil with the consequent the leads for the windings aresecured. The coil 100 disadvan a s pointed out above. The necessity isherein shown with the low impedance winding of applying the windings onseparate machines 5 on the inside of the coil, which is the preferred isalso a material disadvantage. construction, but it is to be understoodthat the With the foregoing in View, it is an Object of coil may asreadily be constructed with the posimy invention (20 effect 8.lBdllCliiOl'l in the size 0f tion of the windings interchanged. 105

a transformer coil of given p y. y a novel constituting a part of thebody structure is a arrangement and construction of t windings hollowcore 7 made substantially rectangular and body structure of the coil. inoutline so as to fit closely about the rectangular Another object of theinven is th Provision leg of the core of the transformer upon which theof a novel body structur for the coil, which so coil is mounted. Thecore '1 is not a reformed 1 0 and cured core, as commonly employed inthe winding of coils on automatic machines, but is formed on the mandrelof a manual winding machine by the operator as the first step in thebuilding up of the coil. This insures that the core '7 is the propersize and that it has not shrunk from too long exposure to the atmospherebefore use.

The core '7 is formed from a strip of gummed insulating paper, known tothe trade as gumcraft, or any other suitable gummed material such asarmite. This strip corresponds in width to the length of the coil to beconstructed, and is of such length that when wound about the mandrel itwill produce a core composed of a pluraiity of layers of paper, thuslending stiffness and rigidity tothe core. The strip so cut to thedesired length and width, is moistened by the operator and then tightlywound about the mandrel of the winding machine. In order that the coreso formed may be as nearly rectangular as possible, the paper is creasedat the corners of the core in a manner such as to cause the sides of thecore to hug the mandrel closely. Herein the core is shown as composed oftwo layers of the gummed paper except for one side which has a thirdlayer formed by the outer end of the strip (see Figs. 2 and 3). Thissmall number of layers is possible because the rigidity of the core 7 isincreased by a construction presently to be described. The core soformed from the gummed strip is immediately employed in the constructionof a coil without first subjecting it to the usual steps of baking,drying, etc., involved in the curing process. In addition to eliminatingthe steps of the curing process, the use of an uncured core also has theadvantages that it facilitates the construction of the coil andeliminates the waste due to the unequal shrinkage of the core and otheruncertainties of the curing process.

Pasted to the outer sides of the core '7 substantially in the middle ofeach of its long sides and extending axially thereof, is a strip ofgummed paper 8 while a strip 8 is similarly attached to each of theshort sides. The strips 8 and 8 are substantially longer than the core'7 and form a skeleton structure binding the windings of the coil. Inaddition to constituting a means for binding the windings, the strips 8and 8'- are made of heavy material and thus also serve to strengthen andmake more rigid the sides of the core '7 thereby preventing a wrinklingof the sides by the pressure of the windings. The strips attached to thecore '7 on those sides thereof whose end edges abut the core of thetransformer when the coil is mounted thereon, herein the strips 8, aremade substantially wider than the sides of the core 7 to which they arepasted in order to insulate the windings from the core of thetransformer as will hereinafter more clearly appear.

Upon the core '7 and the strips 8 and 8 so assembled, the low impedancewinding 5 is formed. The low impedance winding 5 as well as the highimpedance winding 6 are solidly wound, that is, each winding is composedentirely and only of turns of wire with successive turns and turns ofadjacent layers in bodily contact, and does not have paper stripsinterposed between successive layers of turns. A winding so formed isvery compact and requires very little skill in winding because no highdegree of exactness or uniformity in the positioning of the successiveturns is required. In a winding so formed the outer turns of the windingmay be flush with the end of the core, thereby making the windingcoextensive with the core and eliminating the unused length of corecommon in present constructions and which only causes waste space whenthe coil is mounted on a transformer. The end turns are retained on thecore '7 during the winding operation in any suitable way as by means ofside plates (not shown) positioned on the mandrel at the ends of thecore. The side plates have circumferentially spaced slots formed thereinthrough which the ends of the'strips 8 and 8 project.

The winding 5, being composed of a wire of substantial size and havingsubstantial tensile strength, is secured at its inner and outer ends 9and 10 respectively which ends are brought out from the coil to formleads therefor. To secure the inner end 9 of the winding 5, it is placedaxially of the core between the second and third layers thereof and witha portion projecting from one end to form a lead (see Figs. 2 and 3).The end of the winding is thus securely anchored especially againstbeing pulled out by force applied to the portion projecting from thecoil. The end thus held also facilitates bending of the winding over thethird layer of the core (see Figs. 2 and 3), and at right angles to theportion secured in the core to form the first turn of the winding. Asthe turns of the winding increase, the end becomes more and moresecurely held by the pressure of the winding.

The outer end 10 of the winding is bent to project from the end of thecoil opposite that from which the end 9 projects and is secured by oneof the strips 8 which is wrapped around the winding 5 to bind it to thecore '7 and to retain the end turns in position. The other of the strips8 is also wrapped around the winding 5 thus securely binding the windingon opposite sides. The strips 8 are of suflicient length that whenwrapped around the winding 5, the ends overlap and may thus be securelypasted together. If desired, the strips 8 may also be wrapped around thewinding 5 but the preferred construction is to wrap only the strips 8,as here shown.

With the low impedance or secondary winding mounted next to the core '7,a shorter mean length of turn is obtained,-thereby materially decreasingthe direct current resistance, which constitutes a substantialproportion of the total impedance of the winding because of thecompartively few turns. This reduction in resistance may be takenadvantage of by employing a smaller wire and increasing the number ofturns up to, the limit of total resistance permissible, which additionalturns, because of the smaller wire, require no additional space.

Wound over the winding 5 and the overlapped strips 8 is acircumferential strip 11, also of gummed paper, further binding thewinding 5 and insulating it from the primary winding 6 which is to bewound thereover. corresponds in width to the length of the coil and maybe wound about the winding 5 any desired number of times. Herein, oneturn is shown which is ample to insulate the windings'from one another.This strip 11 also has secured to it skeleton strips 12 on the longsides of the coil.

0n the foundation so formed the primary 6 of the coil is wound in themanner previously described. The primary being a high impedance windingcomposed of extremely fine wire requires its ends to be brought out fromthe coil by special leads of heavier wire with which the ends of thewinding have an electrical connection. In se- The strip 11 curing theleads for the high impedance winding, the body structure of the coil isagain employed in a unique manner to effect the anchoring of the leads.The inner end of the winding 6 is soldered (indicated in the drawing aswound about the heavier wire) to a lead 13 which extends axially of thecoil between the strip 11 and one of the skeleton strips 12. Preferablythe lead 13 is located on the side of the coil opposite the side inwhich the ends of the secondary winding 5 are anchored. The lead 13 iscompletely covered by the strip 12 and thus prevents the lead or thesolder thereon from rupturing the thin insulating coat of varnish on thewire composing the winding. Though the portion of the lead 13 secured inthe coil is straight, the pressure of the winding 6 securely retains thelead against normal force tending to withdraw the same.

When the winding 6 so secured at its inner end is completely wound, thestrips 12 are wrapped tightly about the winding to bind it securely andto retain the end turns in position. Like the 'strips 8, the strips 12are of sufficient length that when wrapped about the high impedancewinding 6 their ends overlap to permit them to be tightly pastedtogether. The ends of the strip 12 so overlapped also form an insulatingstrip extending across the entire winding for protecting the windingfrom short circuit by a lead 14 having electrical connection with theouter end of the winding 6 and conveniently placed on the strip 12. Thelead 14 is positioned to project from the end of the coil opposite thatfrom which the lead 13 projects.

The strips 8 previously secured to the outside of the core 7 so as tolie beneath even the secondary winding 5, are now also wrapped aroundthe windings and the overlapping ends pasted together thereby bindingboth the primary and secondary winding to the core. It will also be seenthat the strips 8 when so wrapped about the windings and because oftheir width positively prevent contact between the core of thetransformer and the end turns of the windings. The strips 8 are,therefore, of a comparatively thick stock so as to protect the windingsagainst abrasion by the core of the transformer and to effectivelyinsulate the windings therefrom. The strips 8 thus serve the threefoldpurpose of adding rigidity to the core, binding the windings, andinsulating the end turns of the windings from the metallic core of thetransformer.

To retain the lead 14 in position on the strip 12 and to form aprotecting means for the high impedance winding 6, a cover strip 15 iswound about the coil circumferentially thereof. The strip 15 is wideenough to cover completely the entire length of the coil and thusprotects the surface of the primary winding 6 from injury. One thicknessof the strip 15, when formed from comparatively heavy stock issuflicient for all practical purposes. The lead 14 is further anchoredagainst being pulled out of the coil by a hook 16 which is formed on itsinner end and which engages the strip 15. The hook 16 is pref-- erablyconcealed by an overlapping end portion of the outer covering strip 15.

The substantially complete coil is then removed from the mandrel andinsulating sleeves 17 threaded over the leads 13 and 14 and the ends 9and 10 of the secondary winding. These sleeves are retained on the leadsand the coil further bound together by a third set of skeleton strips 18pasted to the inside of the core '7 on the long sides thereof andwrapped around the entire coil.

Since the rigidity of the coil is not relied upon to retain the endturns of the respective windings in position, such turns beingpositively retained by the skeleton strips, the insertion of strips ofpaper between the successive layers of turns necessary in formerconstructions is entirely avoided with a consequent decrease in radialthickness of the coil. The construction described also obviates thenecessity of winding the coil with the high degree of precision andaccuracy required where paper strips are inserted between successivelayers of turns. With each coil individually and substantiallycompletely formed on a single core and the same machine, the turns ofthe windings may extend to the very edge of the core '7, where they areretained by the side plates on the mandrel while in the machine and bythe skeleton strips which form bands encircling the winding whencompleted. Thus the radial thickness as well as the length of the coilis reduced.

I claim as my invention:

1. A coil comprising, in combination, an uncured core composed of acircumferentially wound strip of gummed paper, and a winding formed onsaid core, the inner end of said winding extending axially of said corebetween the turns thereof and projecting from the end thereof.

2. In a transformer coil having primary and secondary windings, a corecomposed of a circumferentially wound strip upon which said windings aremounted in superimposed relationship, one end of the winding mountednext to said core projecting from the core and, extending axiallybetween the layers thereof to be thus secured, and means for bindingsaid windings to said core.

3. In a transformer coil having a high and a low impedance winding, acore upon which the windings are mounted in radially spaced relationcomposed of a circumferentially wound strip, the low impedance windingbeing mounted next to said core and having its inner end projecting fromsaid core and extending axially between the layers thereof to be securedthereby, a skeleton strip secured to said core and binding the outer endof the winding also projecting from the coil, and means binding saidhigh impedance winding.

4. In a transformer coil having solidly wound primary and secondarywindings in superimposed relationship, a body structure for the coilcomprising a core, a set of skeleton strips pasted to the core to extendaxially thereof and binding one winding onto the core, a circumferentialstrip, interposed between the windings, a set of skeleton strips pastedto said circumferential strip and binding the other winding, and anouter circumferential strip and leads extending axially of the coilbetween said skeleton strips and circumferential strips to be therebysecured in said body structure and electrically connected to the ends ofthe outer one of said windings.

5. A transformer coil comprising, in combination, a core, a lowimpedance winding formed on said core, a circumferential strip woundabout said winding, a skeleton strip secured to said circumferentialstrip to extend axially of the coil, a high impedance winding formed onsaid circumferential strip and bound by said skeleton strip, and a leadelectrically connected with the inner end of said high impedance windingand extendstrip interposed between said windings, a skeleton stripsecured to said circumferential strip and encircling said high impedancewinding to bind the same, a cover strip wound around the coil, and alead having electrical connection with the outer end of said highimpedance winding and extending axially of the coil between said coverand said skeleton strip, said lead having a hook at one end engagingsaid cover.

'7. A coil comprising a gummed paper core substantially rectangular inoutline, a solidly wound winding on said core, and strips of gummedpaper pasted to the sides of said core to extend axially thereof andadapted to be wrapped about said winding to bind the same, one of saidstrips being wider than the side of the core to which it is pasted.

8. In a transformer coil having primary and secondary windings mountedin superimposed relationship, a body structure of insulating materialcomprising a core substantially rectangular in transverse cross-section,a skeleton strip secured to each of two opposite'sides of said core andbinding the inner one of said windings and a skeleton strip secured tothe remaining sides of said core and binding both of said windings, saidlast mentioned strips being wider than the sides of the core to whichthey are secured.

9. In a transformer coil having primary and secondary windings mountedin radially spaced relationship, a body structure of insulating materialcomprising a core substantially rectangular in transverse cross-section,a skeleton strip pasted to each side of the core to extend axiallythereof, said strips being adapted to encircle at least one winding tobind the winding to said core, a circumferential strip interposedbetween the windings, skeleton strips pasted to said circumferentialstrip and adapted to bind the outer one of the windings, a cover stripencircling the coil, and skeleton strips secured within the core andextending around to bind the cover strip.

10. A coil comprising an uncured core composed of a strip of gummedpaper wound to form a plurality of layers, and a winding on said corehaving its inner end portion interposed between adjacent layers of thecore and projecting from one end of the core to form a lead.

11. A coil comprising an uncured core composed of a strip of gummedpaper of a width substantially equal to the length of the coil to beformed and of a length adapted when wound upon a mandrel to form aplurality of layers, a plurality of gummed paper binding strips pastedon the outer sides of said core and of a length substantially greaterthan the length of the core, said strips serving to stifl'en the core,and a winding having its inner end portion anchored to the core andprojecting from one end thereof to form a lead, said winding beingcomposed of a wire wound upon the core with successive turns forming aplurality of directly superimposed layers,

and said binding strips having their end portions wrapped about the endsof the winding and secured together to bind the winding onto the core.

12. The method of making coils which comprises wrapping on a mandrel astrip of gummed paper of a width substantially equal to the length ofthe coil to be formed and of a length adapted to iorm a core having aplurality of layers, pasting on the outer sides of the core while stillon the mandrel a plurality of binding strips extending axially of thecore and having opposite end portions projecting beyond the ends of thecore, inserting one end portion of a wire beneath the outermost layer ofthe core and then winding the wire on the core over said binding stripsto form a coil, and wrapping the ends of the binding strips around theends of the coil to bind them onto the core.

13. The method of making coils which comprises wrapping on a mandrel astrip of gummed paper of a width substantially equal to the length ofthe coil to be formed and of a length adapted to form a core having aplurality of layers, pasting on the outer sides of the core while stillon the mandrel a plurality of gummed paper binding strips extendingaxially of the core and having opposite end portions projecting beyondthe ends of the core, winding on said core over the binding strips aplurality of turns of wire to form a coil with the inner end portion ofthe wire projecting from one end of the core to form a lead, and

wrapping the ends of the binding strips around and binding the windings,the ends of the heavy winding projecting from the coil to form leadswith the inner end of the winding secured between the layers of thecore, and lead wires secured by the circumferential and skeleton stripsand connected to the ends of the fine wire winding.

15. A transformer coil comprising, in combination, a core, a winding onsaid core, circumferentially spaced skeleton strips secured to said coreand encircling said winding to bind the same onto said core, a coverstrip wound around the winding, a lead having electrical connection withthe outer end of said winding and extending axially of the coil betweenthe cover strip and a skeleton strip, and a hook formed onone end of thelead and engaging one of the strips between which it is positioned.

JAMES C. SNELL.

